In the manufacture of glass containers by a forming machine of the I.S. ("individual section") type, one or more streams of molten glass flow downwardly from a feeder bowl of a glass melting furnace forehearth toward a section of the molding machine, and each stream is severed or sheared into a multiplicity of individual gobs by a shearing device positioned between the feeder bowl and the molding machine section. A typical shearing device of the foregoing character includes an opposed set of shear knife elements, each set of shear knife elements being mounted on a carriage assembly, and driving apparatus for reciprocating each of the carriage assemblies toward and away from one another. A shearing device of this general character is disclosed in U.S. Pat. No. 4,813,994 (Kulig). Heretofore, such driving apparatus typically utilized a mechanical cam arrangement in the driving of the carriage assemblies. Such a cam arrangement inherently is limited in the speed that can be imparted to the carriage assemblies, and this speed limitation can act as a capacity limitation on the forming machine. Further, in such a cam arrangement the contact time between the shear knife elements and the glass stream(s), which is an important factor in the quality of the shearing action, cannot be adjusted without suspending the operation of the forming machine to permit a change in the cams.